A Hangman's fracture
is the colloquial name given to a fracture of both pedicles or pars interarticularis of the axis vertebra (C2
The mechanism of the injury is forcible hyperextension of the head, usually with distraction of the neck. Traditionally this would occur during judicial hanging, when the noose was placed below the condemned subject's chin. When the subject was dropped, the head would be forced into hyperextension by the full weight of the body, a sufficient force to cause the fracture.
In the modern world, this injury is still sometimes seen, due to sports injuries or road traffic accidents. In deliberate or suicidal hanging, asphyxia is much more likely to be the cause of death.
A common sign is a constricted pupil (Horner's syndrome) on the ipsilateral side due to loss of sympathetic innervation to the eye, caused by damage to the sympathetic trunk in the neck.